Earlier, class for any Catalog object used to be Products.ZSQLCatalog.SQLCatalog,
but now as we have shifted SQLCatalog to ERP5Catalog, the catalog objects have
lazy_class 'erp5.portal_type.Catalog' as their 1st class in mro. This class
don't have the required attributes.

The lazy_class is dynamic, so its not possible for them to save reserved IDs
as their attributes. So, we use the next class in mro, which would be
class 'Products.ERP5Catalog.ERP5Catalog' and save attributes in it.

Notice that this change of 'self.__klass__' is not required if
we are starting a lock with '_reserved_uid_lock' and then acquire-release it
consicutively in one go(transaction).